Support devices are generally located in pairs on the underside of semi-trailers in their forward areas, and are always used when the semi-trailer is separated from its tractor and is parked by itself. In systems of the prior art, on semi-trailers with air springs, air will almost inevitably have escaped from the springs after the semi-trailer has been parked for a more or less long period of time, as a result of which the rear portion of the semi-trailer droops and the semi-trailer assumes a diagonal position or a position in which it tilts toward the rear in relation to the ground. For this purpose, the support bases or their base plates must be able to swivel, to compensate for this inclined position. The same requirement applies if the semi-trailer is parked on ground that is uneven or not level. In addition to the pivoting capability of the base or of the base plate, it is desirable that, as the support devices are being extended, the movable parts of the support device come to rest gently on the ground so that they are not damaged. For this purpose, corresponding damping elements are located in the support bases.
Because it is very difficult to satisfy all these peripheral requirements with only one model of the base, the general practice is to install different model bases as a function of the conditions in which they will be used.
The required model must generally be defined prior to the purchase of the support winch, because the support base is a component of the winch, and must accordingly be mounted on it.
The different realization of the base generally also requires different arrangements and preparatory steps on the support winch itself. Consequently, there is a specific model of support winch for each type of base. This has the advantage that the base and the support winch can be optimally coordinated with each other, although that, too, has several disadvantages.
For example, during the process of manufacturing the support winch, a great many different manufacturing operations have to be performed for each model, which entails a correspondingly high cost for tools, jigs, inventories of material, space and logistics. Moreover, once the support winch has been manufactured, it is generally no longer possible for the final consumer or the retail dealer to exchange different base models for one another.
It is therefore desirable to develop different model bases that can be used in as many applications as possible, and accordingly have a wide range of potential applications.
The prior art includes one model of a foot which is essentially a rigid structure which has a plate-shaped ground contact surface and can pivot around an axle which is mounted horizontally in the inner tube of the support winch, transverse to the direction of travel. The support foot can adapt to certain inclinations of the road, e.g. entrance ramps, hills and similar inclinations, and can thus be used to park the semi-trailer.
As a result of the inherently rigid realization of the support base, however, impact loads of the type that occur, for example, during the shunting of the semi-trailer, are transmitted directly to the support winch and indirectly to the vehicle. Ultimately, these impacts can lead to disruptions in operation or even damage to both the winch and the vehicle.
To reduce such damage or to eliminate it altogether, there are models of bases that have elastic elements that absorb the kinematic energy of the impact and can thus protect the mechanical components.
DE 31 19 359 A1 discloses a support device in which, on the lower end of the support part to be deployed, there is a ground plate that projects laterally beyond this support part, whereby between this ground plate and the base plate there is an elastic pressure body which is designated the damping element and is made of rubber. A retaining ring that is welded to the base plate has an upper peripheral segment that overlaps and grips the laterally projecting ring-shaped portion of the ground plate, whereby there is a certain amount of play between the retaining ring and the extendable support part. The pivot angle and the deflection travel of the base plate are limited by the compressibility of the elastic pressure body and the distance between the retaining ring and the extendable support part. In this support device there is no pivot bearing. This design gives the base plate only a limited ability to adapt to major uneven spots in the ground, whereby the damping element is deformed both when the base is set down in the vertical direction, as well as when the base is tipped.
EP 0 430 643 A2 discloses a support base, in which the fastening to the base receiving device is identical with the pivot bearing of the base. A tubular bearing element is located in a rectangular housing of the base retaining device and is held so that it can move vertically in slots in two vertical plates that are fastened to the base plate. Between the housing and the base plate there is a damping element which is compressed when the base is set down. An additional deformation in the transverse direction occurs when the base pivots, as a result of which the housing must be pushed over the damping element. This arrangement has a number of disadvantages.
The damping element is exposed to significant and different loads, which leads to rapid material fatigue. The pivoting process is prevented and limited by the damping element. When the support base is retracted, it remains in its pivoted position, because the damping element prevents it from pivoting back into its initial position. When the support base is lowered again, the damping element can interfere with the free movement of the base and damage it.
U.S. Pat. No. 3,666,290 describes a support base in which there are two damping elements between a plate attached to the end surface of the support tube and the base plate. Above the damping element, there is a pivot bearing which consists of a bolt inserted through the support tube, which is oriented so that it can move in two slots of two vertical plates fastened to the base plate. In this arrangement of the support base, too, the damping elements are additionally deformed during pivoting, as a result of which the pivot angle is limited.